serial: 8250_of: Add nuvoton,wpcm450-uart

Add a compatible string for the UART inside the Nuvoton WPCM450 SoC.
It works the same as the UART in NPCM750.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20210320181610.680870-10-j.neuschaefer@gmx.net


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>